Extract Contours

Use the Extract Contours form (model > Maps & Reports > Contours) to extract contours from a surface with a suitable property. This can, for example, be the output of the 3D Grid to Contours form, but it can also be any other property on a surface that can be contoured, including imported data. The form provides additional options to select which time steps or realizations to include, as well as defining the threshold (or multiple thresholds), smoothing and visualization options on the extracted contour polylines.

To extract contour polylines from a surface:

Select a Model, a Surface, a Representation (supported: 2D Grids or Tri-meshes) and a suitable Property on this surface, for example a CO₂ concentration in a CCS simulation.
On the Settings tab, select the options to extract polyline contours from the surface and the property.
1. Choose whether to use a single threshold, or to extract contours at a range of thresholds.
  1. Set a Threshold value at which you want to extract contours. Only positive values are allowed.
    Set the threshold low enough to include all data you want captured within the contour, but high enough to avoid artifacts. For example, if you are interested in values above 0, you would typically choose a threshold close to 0. However, setting it too close can make small mapping artifacts and numerical instabilities have a larger impact, which may introduce unwanted artifacts.
    On the other hand, choosing a threshold that is too high or too low can result in no contour being detected for those values, meaning no contour is extracted. Because the optimal threshold strongly depends on the specific data, there is no single recommended value. It is therefore best to experiment to determine a suitable threshold for your case.
  2. Select Multiple contours and specify values for Minimum, Maximum and Interval to extract polylines at multiple values. This can, for example, be used to visualize the concentration distribution of a plume on a map at a single time step. Only positive values are allowed.
    Important This setting can create a large number of polylines, especially when combined with multiple time steps, so it should be used with caution. For example, when you extract at 10 interval values for 10 time steps, this will already produce 100 polylines, and the total can increase quickly.
2. The Treat undefined values as setting must be specified so the algorithm knows how to handle undefined values in the source property. It is recommended to choose a value that results in smooth contours without introducing additional artifacts. In many cases, keeping Treat undefined values as at 0 (the default) works well. However, depending on the data type and structure, other values may be more appropriate.
3. Prefix/Folder is used as the folder name (in Data in the JewelExplorer) for the extracted polylines. Providing this name is mandatory.
4. You can choose to smooth contours as a post-processing step by de-spiking them. Enable this option by selecting De-spike contours and setting a Gradient threshold, with a default value of 20 degrees. For more details, see the section on the De-spiking polylines tools. By default, smoothing is enabled.
5. Optionally, you can create a CoView with a default framework to display the created contour polylines on a map. This can be used as a starting point for producing high quality maps, for example of a CO₂ plume. This works best when too many contours are not displayed at the same time.
When a property with time steps or realizations is selected, the Steps tab allows you to choose which time steps or realizations are used for contour extraction. This enables you to create contours only for the intervals of interest. The Step Selection Tools can assist in making this selection. For more information, see Managing time steps and realizations.
Press Apply or OK to run with the selected settings. Depending on the model size and complexity, this can take a while.

When finished, the contour polylines are available in the Data folder in the JewelExplorer (with the defined Prefix/Folder name). If the Create CoView option is selected, it will open automatically and display all created contour polylines. You can retrieve the settings used for contour extraction from the Audit Trail.